Stage lighting luminaires, often called instruments in the lighting profession, and are used for lighting performance centers, stages, multifunctional halls, exhibition halls, restaurants, bars and other indoor and outdoor venues where performance, music and pageantry take place or where it is desirable to place lighting on an object or scene.
Typical stage lighting involves lights having a directional beam with a light source that is directed onto the stage in order to provide lighting for the performance. Conventional fixed and moving head lights and down-lights are also used. When light sources, such as compact fluorescent lamps or LEDs (light emitting diodes) with broad distribution patterns are used in down-lights, luminaire efficiency tends to be relatively low, with an average efficiency typically less than 60%, which may be due to light losses within the lighting apparatus. The possible range of sizes and shapes of reflector design are typically limited by the geometry of the housing, lamp placement, and the luminaire's light distribution considerations. A large percentage of light emitted from the light source may become trapped/absorbed within the fixture housing and may be significantly attenuated by multiple reflections before exiting the luminaire.
Theatrical lights or instruments typically have ellipsoidal reflectors and lenses, spherical reflectors and lenses or parabolic reflectors with or without a lens. These instruments, sometimes also called lanterns (UK), have various features including framing shutters, adjustable beam width, and soft edged or more defined beam edges. In the last 15 years or so, “moving lights” have also been introduced more widely for music performance and theatrical use, some of which may include remote control of color, beam-width, pan, tilt, flashing, intensity and various ‘gobo’ patterns that allow variation in beam pattern and shape. The gobo patterns may also be rotated by remote control.
Parabolic reflectors, when used in accent lighting, generally narrow the beam so as to concentrate the light on a particular area of interest to be illuminated as in an isolated museum display. The effectiveness which a reflector has at concentrating the light beam in a specific direction is related to the size of the luminous source and the distance between the source and the reflector and its shape.
The effectiveness or efficiency of any given luminaire is governed mainly by two factors. The first factor is related to the intrinsic efficiency of the light source, which is related in lumens per watt, meaning the number of watts of power that it takes to produce a certain number of lumens of light. The second factor is dependent upon the desired output beam pattern of the fixture in question.
Parabolic Aluminized Reflector lights, or PAR lights, or PAR cans, are used when a substantial amount of lighting is required for a scene. A PAR can is a sealed beam PAR lamp housed in a simple can-like unit. The reflector is integral to the lamp and the beam spread of the unit is not adjustable except by changing the lamp. PAR lamps are widely used in architectural lighting. PAR lights have seen heavy use in rock and roll shows, especially those with smaller budgets, due to their low cost, light weight, easy maintenance, high durability, and high output. They are often used in combination with smoke or haze machines which make the path of the beam visible. They are also often used as top, back, or side lights in the theater and for special effects. All PAR lamps except those with narrow or very narrow lenses produce an intense oval pool of light, some with fixed focus and soft edges. In order to adjust the orientation of the oval, the lamp must be rotated.
Scoop lights or scoops are circular fixtures that do not have any lenses. They have an ellipsoidal reflector at the back of the fixture that directs the light out of the fixture. Since they do not have any sort of lens system they are cheaper than other fixtures. However, the light cannot be focused at all. Scoops are most often used to flood the stage with light from above, or to light backdrops and are occasionally used as work lights.
LED stage lights are stage lighting instruments that use light-emitting diodes (LEDs) as a light source. LED instruments are an alternative to traditional stage lighting instruments which use a halogen lamp or high-intensity discharge lamps. Like other LED instruments, they have high light output with lower power consumption. Most LED fixtures utilize three or more colors (usually red, green, and blue) which can be mixed to hypothetically create any color. LED stage lights come in four main types—PAR cans, spotlights, strip lights, and moving head lights. In LED PAR cans, a round printed circuit board with LEDs mounted on is used in place of a PAR lamp. Moving head types can either be a bank of LEDs mounted on a yoke or more conventional moving head lights with the bulb replaced with an LED bank. Most shows use LEDs only for lighting cycloramas, or as top, side, or back light due to their low throw distance. They can also be used as audience blinders (lights pointed directly at the audience from a low angle). Phosphorescent coatings over LED lights can result in light having wavelengths other than those output by the LED.
The ellipsoidal reflector spotlight (ERS), also known as a profile spot (after its ability to project the silhouette or profile of anything put in the gate) (UK) and Découpe (French), is the most abundant instrument type currently in theatrical use. These are sometimes known as a profile spotlight (in Europe) or by their brand names, especially the Source Four (a popular lantern from ETC) and the Leko (short for Lekolite, from Strand lighting). The major components of an ERS light are the casing in which the internal parts are mounted, an ellipsoidal reflector located in the back of the casing, a lamp mounted to position the filament at the rear focal point of the ellipsoid, a dual plano-convex lens (two plano-convex lenses facing each other in the barrel), and at the front, a gel frame to hold the color gel. The light from the lamp is efficiently gathered by the ellipsoidal reflector and sent forward through the gate, shutters and lens system.
Fresnel lantern (UK), or simply Fresnel (US), employs a Fresnel lens to wash light over an area of the stage. The distinctive lens has a ‘stepped’ appearance instead of the ‘full’ or ‘smooth’ appearance of plano-convex lens used in other lanterns. The resulting beam of light is wide and soft-edged, creating soft shadows, and is commonly used for back light, top light, and side light. Another method of controlling the spread of light is to use either a top hat (also referred to as a snoot), which generally limits the light coming out, or a barn door, whose flaps work as though they were shutters on an ERS. These methods limit light output and keep excess light from spilling into the eyes of audience members or where it is not desired. Fresnels use a spherical reflector, with the lamp at the focus point. The lamp and reflector remain a fixed unit inside the housing, and are moved forward and back to focus the light. This is accomplished using a slider on the bottom or side of the lantern, or using a worm track. At very tight focus, the lanterns are the least efficient, as the least light can escape the housing. Therefore Fresnels are not good for tight focus on small areas. They are most often used at medium distances from the stage for area lighting.
The “Source Four Par” (US) is a lighting instrument which combined the design of the PAR fixture with that of the Fresnel. The fixture is more versatile, allowing for a flood or a softer spot. Pebble Convex lanterns are similar to Fresnels, but use a plano-convex lens with a pebbled effect on the planar (flat) side, resulting in less “spill” outside the main beam. They are currently used much more widely in Europe than North America.
A beam projector is a lens-free instrument having very little beam spread. It often uses two reflectors. The primary reflector is a parabolic reflector and the secondary reflector (often omitted) is a spherical reflector. The parabolic reflector directs the light into nearly parallel beams, and the spherical reflector is placed in front of the lamp to reflect light from the lamp back to the parabolic reflector, which reduces spill. The result is an intense shaft of light that cannot be easily controlled or modified. Newer fixtures and PAR lamps have created easier ways to produce this effect. One example of a beam pattern is a conventional sealed beam car headlight where most of the light beams are directed down and out to the road but some light beams escape directly from the light source forward unless partially masked in a wide-angle direction not under the control of the reflector.
Another example is the stage lighting spotlight or followspot (also in architecture called a trackspot, or limelight). The followspot is a lighting instrument that is moved during a performance by an operator or control to provide emphasis or extra illumination and usually to follow a specific performer when he or she is moving around the stage. Followspots contain a variety of operator-controlled optical mechanisms. They may include mechanical shutters, which allow the light to be doused without turning off the lamp, lenses to control and focus beam width, and internal color gels, often in a color magazine. The followspot projects a circle of light onto a performer on a stage from the rear of the hall with very little light spilling beyond the specific area surrounding the performer. The light from the source is either directed by reflectors and or lenses to the area to be illuminated, whatever its size and shape designed, or less desirably, the light from the source is shaded, that is, the light is absorbed or blocked, such that the light cannot escape from the luminaire in an undesirable direction. Followspots are commonly used in musical theater and opera to highlight the stars of a performance, but may be used in dramas well. They are also used in ice rinks and sports venues. In stadiums, sports-lighters with a large reflector and metal halide lamp are considered appropriate for general lighting when used with other similar fixtures on a sports field for sporting or other events. These lighting instruments come in a variety of sizes with light sources ranging from low power incandescent light bulbs to very powerful Metal Hallide arc lamps. Carbon arc lamp spots were common until the 1980s, using the arc between carbon rods as their light source. These followspots require special installations that includes high volume ventilation due to the hazardous Ozone fumes produced by the carbon arc. The hot discharge in xenon arcs creates extremely high internal pressure in the lamp and thus presents a safety concern.
Hydrargyrum medium-arc iodide lamps, designed initially for use in film, are now seen commonly on stage. These instruments produce light with a color temperature similar to daylight (5600K to 6000K). HMI fresnels are most common, but HMI PARs are also available.
These instruments typically require a large amount of power (between 2 kW and 12 kW) and must be dimmed mechanically or with the use of an electronically controlled douser.
Lighting fixtures are also used in architecture. Architectural lighting falls into three broad categories—general lighting, task lighting and accent lighting. The size of the area to be illuminated and the distance between the area to be illuminated and the fixture location or position determine the lighting fixture chosen by the designer. For example, fluorescent lighting may be considered appropriate in a library.
The luminaire system according to the present invention addresses many of the disadvantages of the prior art. The lighting instrument of the invention provides greater control and efficiency than attainable with existing lighting instruments for lighting designed principally to provide near parallel beams for illuminating a specific area from a significant distance. The reflector of the invention allows the source of light to be surrounded more completely than possible with current lighting instruments. This new reflector system redirects more of the source illumination into nearly parallel beams irrespective of the intrinsic luminous efficiency of any light source chosen to be used within the reflector system. Significant distances of greater than 20 times the diameter of the luminaire are possible. The system of reflectors in this invention also allows the beam width to be varied without encountering the increasing absence of light in the center of the beam as compared to conventional parabolic reflectors when the light source is moved. It has been found that 30% to 40% more illumination is achieved by redirecting the luminous output from the light source in accordance with the use of the invention herein.
One embodiment of the apparatus provides a collapsible reflector. An advantage of the collapsible embodiment of the invention includes ease of transport, shipment, and storage rendering it especially useful for traveling performances. Other advantages of the reflector system of the invention will be readily apparent to persons skilled in the art.